An estimated one in four teen women will become pregnant by age 20. Rates are even higher for LGB+ teen girls, who are between two and four times more likely to be pregnant during adolescence. Despite this elevated risk, there is a complete lack of prevention programs tailored to the unique needs of LGB+ teens. The wide adoption of text messaging provides novel opportunities to go where hard-to-reach youth ?are.? Four in 5 adolescents who own a cell phone use text messaging, which is both the primary and preferred mode of communication between peers. Moreover, cell phone ownership is high across SES and race/ethnicity.. This R01 proposal is an extension of our development and evaluation work with Girl2Girl, a text messaging-based pregnancy prevention program designed for LGB+ teen girls 14-18 years of age across the United States. Guided by the Information-Motivation-Behavioral Skills (IMB) Model, the intervention has been iteratively refined within ongoing feedback from 242 LGB+ teen girls recruited nationally in focus groups and content advisory teams. To date, we have reached our target 840 LGB+ girls for the RCT. Among the 327 teens who have completed the intervention thus far, 300 (91%) have completed the intervention-end assessment at 5-months post-baseline. Preliminary data suggest contraception uptake is higher in the intervention group (42%) than the control group (24%; p=0.001). Our Specific Aims for this R01 are: Specific Aim 1: Evaluate the Girl2Girl intervention for its impact on pregnancy preventive behavior over time. LGB+ girls are randomly assigned to Girl2Girl or a control group focused on ?healthy lifestyle? topics. We have reached our target sample size of 840 teens. To date, 928 have been randomized. Enrollment will continue through 12/31/17. Our primary outcome measures are self-reported: use of birth control methods (e.g., the shot), condom use during penile-vaginal sex, and pregnancy. Because 40% of the sample is sexually inexperienced, secondary measures are intentions to have sex, to use condoms, and uptake of other birth control methods. Measures are collected at multiple time points, including 3- and 9-month post-intervention end, allowing for trajectory analysis to examine how the intervention impacts behavior over time. Specific Aim 2: Identify for whom and under which circumstances Girl2Girl works best. Effect modification will be examined to identify youth characteristics associated with increased program impact (e.g., age, sexual identity). We also will examine program features to see if program engagement predicts better outcomes (e.g., number of modules completed, number of messages sent to one?s Text Buddy). Specific Aim 3: Identify opportunities to improve Girl2Girl. We will analyze the self-reported program acceptability experiences and in-vivo feedback from Text Buddy dyads to identify where and how we can improve the intervention for greater impact.